Yes, but that's my point: the ARM2 cannot get faster than 1.25 MIPS in an Amiga because of the memory bandwidth (assuming that the CPU uses 5 MBytes/s of the available 7 MBytes/s that it has to share with the graphics chipset).
That is defently the limitation that you need to improve over time. And eventually you likely split the graphcis memory off from the main memory.
To improve performance you need to start to add cache in or around your CPU/MMU and you need an increasingly clever memory chip to arbitrate memory access.
But you are right, you always going to run into limitations. As RAM is the most expensive part of the BOM, literally anything you can do to get maximum utilily of out of the memory bandwith is where you need to spend design time.
Like ARM did a 16 bit encoding for your 32 bit RISC would have been a great design feature to further reduce the how intensive it is to keep the CPU active. Of course nobody had thought of that combination, that was an early 90s thing.
RAM is just so expensive back then, you build your machine around sharing it as well as you can and living with the downsides.
There was never any ARM-based Amiga from Commodore or any Commodore partner.
Any CPU performance is 100% theoretical because there was no such hardware.
The 68000 performance numbers I cited are from contemporary benchmarks and they _favour_ the 68K. The real chip in real Amigas ran slower.
The Acorn Archimedes used the ARM2; the ARM was developed for the Archimedes range. Its display, sound, memory controller, etc. are all pretty much unaccelerated.
Now there are Arm-based Amigas but they run the Amiberry emulator on top of Linux.
Whole idea behind ARM was running at full speed of ram. Amiga had very little Ram BW to spare for CPU so ARM2 would be throttled by narrow slow ram bus in the Amiga.
To this day my pet peeve is that Commodore didn't ship Amigas with a tiny amount of scratch RAM independent of the shared bus. Would have been so useful.
panick21|4 months ago
To improve performance you need to start to add cache in or around your CPU/MMU and you need an increasingly clever memory chip to arbitrate memory access.
But you are right, you always going to run into limitations. As RAM is the most expensive part of the BOM, literally anything you can do to get maximum utilily of out of the memory bandwith is where you need to spend design time.
Like ARM did a 16 bit encoding for your 32 bit RISC would have been a great design feature to further reduce the how intensive it is to keep the CPU active. Of course nobody had thought of that combination, that was an early 90s thing.
RAM is just so expensive back then, you build your machine around sharing it as well as you can and living with the downsides.
lproven|4 months ago
There was never any ARM-based Amiga from Commodore or any Commodore partner.
Any CPU performance is 100% theoretical because there was no such hardware.
The 68000 performance numbers I cited are from contemporary benchmarks and they _favour_ the 68K. The real chip in real Amigas ran slower.
The Acorn Archimedes used the ARM2; the ARM was developed for the Archimedes range. Its display, sound, memory controller, etc. are all pretty much unaccelerated.
Now there are Arm-based Amigas but they run the Amiberry emulator on top of Linux.
rasz|4 months ago
actionfromafar|4 months ago
lproven|4 months ago
https://en.wikipedia.org/wiki/Amiga_Chip_RAM